The present invention relates to one part heat curable organopolysiloxane compositions having improved shelf stability. More particularly the present invention relates to the employment of a hydrosilylation catalyst in the form of an inclusion compound of a cyclodextrin such as .beta.-cyclodextrin and a complex of a platinum halide and an aliphatically unsaturated cyclic compound such as 1,5-cyclooctadiene.
Prior to the present invention, as shown by Kookootsedes et al., U.S. Pat. No. 3,445,420, one component organopolysiloxane compositions were based on a platinum catalyzed silicon hydride-silicon vinyl addition reaction which generally utilized an inhibitor for the platinum catalyst. The purpose of the inhibitor was to slow down the hydrosilylation reaction to increase the work life of the one component organopolysiloxane mixture at low or room temperatures. The organopolysiloxane mixtures were generally composed of a base polymer consisting of a polydiorganosiloxane having chemically combined methylvinylsiloxy units which was used in combination with a siliconhydridesiloxane. Additional inhibited one package silicon hydride-silicon vinyl one package platinum addition curable organopolysiloxane compositions are shown by Berger et al., U.S. Pat. No. 3,882,083, utilizing an ethylenically unsaturated isocyanurate as an inhibitor, and U.S. Pat. No. 4,472,562 and 4,472,563 employing acetylenic unsaturated inhibitors.
In copending application Ser. No. 07/364,557, filed May 22, 1989, one part heat curable organopolysiloxane compositions are described utilizing platinum catalyst which is microencapsulated in an organic resin, such as a thermoplastic organic polymer, or a thermosetting organic polymer. The microencapsulated catalyst is in the form of capsules having an average diameter of about 4-60 microns. Although satisfactory shelf stability under ambient conditions can be achieved with the use of such microencapsulated platinum catalysts in one part mixtures of a vinyl-substituted diorganosiloxane fluid and a siloxane hydride fluids, it has been found that the capsules often settle to the bottom of the one part heat curable organopolysiloxane mixture, or reduce the transparency of the curable mixture.